This invention relates to a navigation system adapted to display map information and present position information in that map information to support or back up driving of a moving body such as an automotive vehicle, etc., and more particularly to a navigation system provided with means adapted to store locus data of a route or path through which a moving body has passed to carry out reference display of that movement route.
In a navigation system adapted to be mounted in a vehicle, such a method is employed to determine a present or current position by use of position determination means such as GPS (Global Positioning System), etc. to display a map including the determined position and display a position of the vehicle itself moving every moment in that displayed map, and to store locus data of a route or path through which the vehicle has passed, thus to carry out display of a present position and display of a locus of the transit route up to the present position.
In this kind of navigation system, the locus data are collected by storing in succession determined present position data every fixed time or every movement of a fixed distance into a ring buffer memory of a fixed memory capacity. At the stage where the quantity of those collected locus data exceeds the memory capacity of the ring buffer memory, new data are overwritten onto the stored locus data in the order from old locus data. Thus, a fixed quantity of locus data are constantly kept collected. Then the display of locus, display of a locus is performed by use of the local data stored in that ring buffer memory. Accordingly, there was adopted a display system such that a locus of a zone or division of a fixed range determined by a memory capacity of the ring buffer memory immediately before a present position of a route or path through which a vehicle has Just traveled, is displayed.
In such storage of locus data and display of a locus, in the case of attempting to leave past locus data, it is desirable to store locus data over a movement path as long as possible, thus making it possible to make reference to those locus data. However, in the above described system, when an attempt is made to allow a quantity of locus data which can be stored to be more than that of the existing one, thus to elongate a movement path which can be referenced to, the capacity of the ring buffer memory must be increased. Thus, there result nothing but increased cost and size of the system.
Further, in utilization for an automotive vehicle, etc., movements to various destinations are frequently carried out. There take place many times instances where one goes for a second time to a designation where one has been once. Ordinarily, in the case of movement by an automotive vehicle, etc. to a designation, one cannot readily memorize a route even if one has been only once. For this reason, several times of traveling are required until one can go to a designation without losing his or her way. In addition, in the case of movement to places where one seldom goes, the human memories of the route to the destination may fade or vanish. Therefore, although one has been to that place once, there occurs the necessity of confirming the route to that designation by making reference to a map before one goes to that destination or on his way to that destination.
As stated above, the information as for the route through which an automotive vehicle has traveled once is greatly beneficial in the case where it travels next. In the display of a locus, however, through a locus of a path through which an automotive vehicle has already traveled is displayed only a locus of a zone or division of a fixed range of a path through which an automotive vehicle has traveled to a present position, can be as displayed.